Active markers (e.g., LED markers) emit a trackable signal without the need for an external light source. Typically, such markers obtain power, for example, from an external power source via a cable connection or via an internal battery pack. Thus, instruments which are fitted with such active markers either have a cable attached thereto or are supplied with energy by batteries or power packs.
Cables can be problematic, as they tend to obstruct the work area and/or make it difficult to handle the markers and/or instrument. Batteries or power packs, on the other hand, can be heavy and/or difficult to sterilize. Further, active LED markers have the disadvantage of a narrow emitting angle.
Passive markers, such as are known for example from DE 196 39 615 A1, solve the handling and sterilization problems associated with active markers. However, manufacturing such passive markers can be relatively complicated, as a reflective covering generally is formed over such markers. Further, a significant amount of manual labor is involved in creating such markers.